Computer network performance can be impacted by factors relating to the devices that communicate through the network. Particular network nodes, e.g., computer workstations, may monopolize the network""s limited bandwidth by transmitting a large number of packets. This consumption of bandwidth can be caused by the execution of application programs that require the bandwidth, or it can be sometimes caused by malfunctions in these programs. For example, communicating computers commonly issue acknowledge packets to signal the receipt of a packet, and the failure to properly process the acknowledgment will usually cause the sending computer to repeatedly retransmit the original packet. Problems may also arise with network communications devices, e.g., hubs, switches, bridges, and routers, that facilitate the inter-node communications. These devices may malfunction by incorrectly forwarding packets between the separate communications links that the devices maintain. When those scenarios occur chronically, a large portion of the bandwidth can be needlessly wasted.
Different types of performance-impacting problems can arise with the media that is used to transmit the messages between network devices. The shielding in twisted pair and coaxial cables may be damaged, connectors may have oxidized, or devices may improperly electrically interface to the media. Each of these problems can interfere with the electrical signal transmission and lead to transmission errors, which necessitates the retransmission of packets and thus the consumption of bandwidth.
A class of devices has evolved to diagnose problems occurring at the software layer, in the seven layer open systems interconnection (OSI) reference model. Protocol analyzers and remote monitoring (RMon) probes are commercially available devices that decode properly formatted digital transmissions on local area networks (LANs). These devices use standard network interface hardware and function as passive network nodes that acquire packets and detect the cable voltages that are associated with collisions in the example of carrier sense multiple access with collision detection (CSMA/CD) type networks. The origin, destination, and number of packets can be determined by reference to the packets"" headers and bandwidth utilization statistics accumulated. The number and frequency of collisions can also be monitored.
Some problems, however, are invisible to the network analyzers and monitors. Transmissions that do not strictly conform with the network""s protocol, such as invalid packets exposed through error checking, are simply ignored by these devices. In other instances, these protocol analyzers and RMon probes will not capture successive packet transmissions that do not comply with the protocol for the inter-frame gap, i.e., the minimum time allowed between successive packet transmissions. These devices will chronically miss the second in-time packet.
Time domain reflectometry (TDR) techniques can be used to analyze the network""s physical layer. According to the technique, a pulse of a known shape is injected or launched onto the cabling of the network. As this pulse propagates down the cable and hits electrical xe2x80x9cobstacles,xe2x80x9d or changes in the cable""s characteristic impedance, echoes are generated that travel back to the point of injection. The existence of the echo can indicate cable breaks, frayed cables, bad taps, loose connections, or poorly matched terminations. The time interval between the initial transmission of the pulse and the receipt of the echo is a function of a distance to the source of the echo. In fact, by carefully timing this interval, the source of the echo can be accurately located. Drawbacks, however, exist in conventional TDR techniques. Generally, they can only be used on non-operational networks. This principally limits TDR to testing networks at the time of installation.
More recently, inventors in the instant application have proposed techniques that solve the shortcomings associated with network analyzers and TDR techniques. This is disclosed in U.S. patent application Ser. No. 08/619,934, filed on Mar. 18, 1996 entitled xe2x80x9cPacket Network Monitoring Devicexe2x80x9d. This application is incorporated herein in its entirety by this reference. The approach described in this application provides for the high speed digital sampling of the communications on the network. In this way, it enables analysis of those signals at the physical layer and in terms of the actual current or voltage transitions occurring on the cabling. As a result, improperly formatted or corrupted transmissions may be decoded and analyzed. This distinguishes it from network analyzers that merely decode properly formatted transmissions. Additionally, the approach also provides for a type of TDR analysis on a functioning network and, as disclosed in U.S. patent application Ser. No. 08/890,486, filed on Jul. 9, 1997 entitled xe2x80x9cMethod and System for Characterizing Terminations in a Local Area Networkxe2x80x9d, which is also incorporated herein in its entirety by this reference, the physical extent of the network is determinable.
The present invention is directed to a cross-connect panel that provides a mechanism for connecting to the signal transmission media of a computer network. In this way, it is compatible with the systems disclosed in the 08/619,934 and 08/890,486 applications, providing a connection to an operational, installed network to allow the monitoring of the separate communication links forming the network. In the typical scenario, the inventive cross-connect panel replaces the common cross-connect panel that receives the various cables running between the remote nodes and the hub, switch, or other network communications device.
Accordingly, the invention provides a series of panel-node connectors that are adapted to receive the signal transmission media from the network nodes, which may be individual nodes in the case of a star topology network with a hub communications device or separate LANs in different collision domains in the case of a switch, bridge, or router communications device. In a typical implementation, each panel-node connector may be realized as a group of wire-wrap pins around which wires from the remote nodes, or similar devices, are wound. The groups together define punch-down channels into which the cables from the nodes are placed in some implementations.
The cross-connect panel also has panel-device connectors that in most embodiments will be of a standard type, RJ-45 in one very specific implementation. The panel-device connectors are intended to link the network communications device to the panel.
The panel-node connectors and the panel-device connectors are electrically interconnected to each other via a backplane to complete the communications links. The backplane could in many specific embodiments be a circuit board or other interconnect that provides separate conductor paths between the connectors. What distinguishes the inventive cross-connect panel, however, is the fact that the panel further includes a monitoring port that is also preferably connected to the backplane to provide physical layer access to the communications links. In this way, a network monitoring device interfacing with the port is connected directly to the network""s communications links or disconnected when monitoring is not necessary.
The above and other features of the invention including various novel details of construction and combinations of parts, and other advantages, will now be more particularly described with reference to the accompanying drawings and pointed out in the claims. It will be understood that the particular method and device embodying the invention are shown by way of illustration and not as a limitation of the invention. The principles and features of this invention may be employed in various and numerous embodiments without departing from the scope of the invention.